title: A kinetically stable plant subtilase with unique peptide mass fingerprints and dimerization properties.
abstract: Milin, a potent molluscicide from the latex of Euphorbia milii, holds promise in medicinal biochemistry. Electrophoresis, size exclusion chromatography, mass spectrometry and other biochemical characteristics identify milin as a homodimeric, plant subtilisin-like serine protease, the first of its kind. The subunits of milin are differentially glycosylated affecting dimer association, solubility and proteolytic activity. The dimeric dissociation is SDS-insensitive and strongly temperature dependent but does not appear to be linked by disulfide bridges. N-terminal sequence of acid hydrolyzed peptide fragments shows no homology to known serine protease. Peptide mass fingerprinting and de novo sequencing of the tryptic fragments also did not identify putative domains in the protein. Milin seems to be a novel plant enzyme with subunit association partly similar to human herpes virus serine proteases and partly to penicillin binding proteins. Its behaviour on SDS-PAGE gels and other properties is like "kinetically stable" proteins. Such subunit association and properties might play a critical role in its physiological function and in controlling Schistosomiasis.
authors.affiliation: Molecular Biology Unit, Institute of Medical Sciences, Banaras Hindu University, Varanasi 221005, India.
authors.forename: Subhash Chandra
authors.initials: SC
authors.lastname: Yadav
authors.forename: M V
authors.initials: MV
authors.lastname: Jagannadham
authors.forename: Suman
authors.initials: S
authors.lastname: Kundu
authors.forename: Medicherla V
authors.initials: MV
authors.lastname: Jagannadham
mesh_terms: D000595:Amino Acid Sequence; D019281:Dimerization; D015180:Electrophoresis, Gel, Two-Dimensional; D004795:Enzyme Stability; D028481:Euphorbia / Q000201:enzymology*; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010446:Peptide Fragments / Q000737:chemistry; D010940:Plant Proteins / Q000737:chemistry* / Q000378:metabolism*; D011487:Protein Conformation; D011489:Protein Denaturation; D017433:Protein Structure, Secondary; D012697:Serine Endopeptidases / Q000737:chemistry; D013381:Subtilisins / Q000737:chemistry* / Q000378:metabolism*; D013696:Temperature
chemical_list: D010446:Peptide Fragments; D010940:Plant Proteins; D012697:Serine Endopeptidases; D013381:Subtilisins; C119297:subtilase, plant